As others have said, health anxiety is not amenable to rational discussion! You have my sympathy TBsNana. However much you discuss it with your husband, it will not help him, it will just intensify his feelings of not being understood. The accepted advice is NOT to discuss it. When he says he thinks he has COVID, simply tell him to get a test and don't discuss it any further. It is a mental health problem, and the best therapy is CBT, possibly with the support of a Beta blocker to get him over the worst. However, CBT is in short supply at the moment. What you could do is ring his GP and tell her/him about the problem, so it is in his notes for whenever he decides to contact them. Of course, the GP cannot divulge anything confidential about your husband to you, but a lot of people don't realise that most GPs are happy to have this kind of information, which they will take into consideration when the patient consults them. This is particularly important with mental health problems. Good luck!